Film tension control device



May 12, 1959 w. s. HILL FILM musmn cowrnoz. DEVICE 2 Sheets-Shut 1 Filed July 1, 1954 INVENTOR h r MW E Wm M N May 12, 1959 w. G. mu. 2,886,257

FILM TENSION CONTROL DEVICE Filed July 1, 1954 2 Sheets-Sheet 2 INVENTOR W/LBUE G. HILL BY u/ 34 ATT RNEY United States Patent FILM TENSION CONTROL DEVICE Wilbur G. Hill, Binghamton, N. asslgnor to General Aniline 8: Film Corporation, New York, N.Y., a corporation of Delaware Application July 1, 1954, Serial No. 440,7 69

9 Claims. (Cl. 242-755) This invention relates to winding of web material of the type which has considerable elasticity, such as film base or similar plastic materials, and more particularly to the control of the windup tension as the windup roll diameter becomes progressively larger in the winding process.

In the manufacture and processing of materials such as photographic film, paper, cloth, plastics and the like, it is customary to wind the material onto a shaft or core. At the beginning of wind the core diameter may be a few inches whereas at the end of wind for the particular roll, the size will be many times that of the core. For film rolls, the finish or outside diameter is usually in the order of three to six times the core diameter. These differences in diameter of roll from start to finish create a problem in winding tension control. In the case of photographic film base stocks and the like which are sensitive to pressure and deformation, the limits of permissible operating tension are relatively narrow.

For winding wide web material such as film base as cast or coated, two systems of drive for winding tension control are commonly used. One produces a constant uniform tension from the start to finish of winding and the other, a constant driving torque. The latter system is rather easily accomplished by using an electric torque motor directly connected to the windup shaft but the tension change is approximately inversely proportioned to the diameter of roll. This causes the tension at the end of winding to be several times less than at the start. For a start to finish ratio of diameters 1 to 4 the tension at the end will be in the order of one-fourth that at the start. In case of the constant tension system, the pull is the same at the beginning as at the end but the torque at the end will be four times that at the start for a 1 to 4 ratio of diameters. With the higher torque at the end, the effective tension in the wraps at the smaller diameters, through which the increase in torque must be transmitted, will be increased. In this situation, if, at the start of wind, the tension and friction between layers is not willciently high, the inner wraps of web will slip under the increased torque and cause telescoping of the roll and other undesirable effects.

For some types of film material it is desirable to wind several thousand feet of stock on a core and exceed even the 1 to 4 ratio. In such instances, the tendency of the roll to telescope" is greater. For example, the tension may be proper to wind up to a 15" diameter on a 3" core, but if the same pull (tension) is maintained on the web as the roll continues to build up further, to say 24", the torque which must be transmitted by the film layers near the core will increase by 60%. In this case the torque at the end of winding is 8 times that at the start. This high torque must be transmitted by the layers near the core which were wound at a much lesser torque. Tightening of the start layers by reason of the higher torque, tends to slip the layers and cause telescoping.

It has been found in practice that neither the constant 'ice tension type of winding nor that of the constant torque gives the most suitable operational features. Rather, a tension curve lying between these two types of operations appears to be the most desired for materials mentioned above. This is particularly advantageous if the machine runs at a constant web speed and the tension is so controlled as to result in a tapered change from start to finish of winding operation.

Accordingly, it is the primary object of this invention to control the web tension in a particular predetermined manner and thereby obtain tapered tension between the start and finish of a winding operation.

A further object of this invention is to provide an instrumentality which, applied to conventional winding apparatus, will modify the windup tension automatically in the desired manner.

It is a particular feature of this invention that the control apparatus is extremely simple and can easily be added to various types of web winding machines used in the industry.

Another feature of this invention is that the control apparatus may be easily adjusted to produce desired operational curves as to windup tension.

Other objects and features will be apparent from the following description of the invention, pointed out in particularity in the appended claims and taken in connection with the accompanying drawings, in which:

Fig. 1 is a perspective view of a portion of a web winding apparatus;

Fig. 2 shows the tension control device in accordance with the invention with the tension regulating lever arm in its near mid-position;

Fig. 3 shows the arrangement of Fig. 2 with the tension regulating lever arm in the start position;

Fig. 4 shows the arrangement of Fig. 2 with the tension regulating lever arm in the near end position;

Fig. 5 shows a modified form of the fluid container affixed to the tension control lever arm in position near mid-point of winding operation;

Fig. 6 shows the arrangement of Fig. 5 with the tension control lever arm in position nearing the end of winding operation; and

Fig. 7 is a perspective view of a modified form of the fluid container used with the arrangements shown in Figs. 1, 2, 3 and 4.

Referring to the figures, the apparatus shown in Fig. 1 is a schematic layout representing the general physical arrangement of significant parts of a web winding machine in order to simplify the illustration and thereby pinpoint the invention. The machine, per se, as to its specific construction, is not material to the invention, the essential condition being that it is of the type which employs a dangle roller (often referred to as a dancer roller) 10, the effective weight of which determines the tension and the position of which controls the speed of the windup roll 11. The web material 12 is fed from a roll cluster comprising rollers 14, 15, 16 and 17 by means of a driven roll 18, the shaft of which is attached to the motor 19. The latter is arranged to drive the roll 18 at a constant Roller 10 is supported between brackets 21 and 22 affixed to the shaft 23. Bracket 22 extends beyond the shaft 23 thereby forming a lever arm and is coupled by the linkages 25 and 26 to the shaft 27 of an electrical speed control unit 28 for the drive motor 29. The latter has its shaft 30 coupled to the shaft 31 of the windup roll 11.

The frame of the machine and other portions not relevant to the invention have been omitted from Fig. 1 in order to simplify the illustration. It should be understood that the rollers and also the shaft 23 are journalled assessor in suitable bearings supported in the frame. The supports 33 and 34 for the motors 19 and 29, respectively, are part of the frame, the cross beam 35 of which is cut away to show the tension control device in accordance with the invention.

The device comprises the lever arm or bar 37 attached to the end of the shaft 23, the latter thereby becoming the fulcrum of the lever. A counterweight 38 is adjustably supported on one end of the bar 37, and an elongated container 39 in parallel with the bar 37 is attached thereto by means of brackets 40 and 41. The container 39 is partially filled with a suitable liquid medium 42 as will hereinafter be described in detail.

Considering the operation of the tension control apparatus, in addition to Fig. 1 reference should be had to Figs. 2,3 and 4 which illustrate in a simplified manner, different operative positions from the start to finish of the winding of the web material. Identical parts of Fig. I bear the same reference characters in the other figures.

Fig. 2 shows the position of the bar 37 at about midway of winding operation. For easier understanding, the dangle roller is shown attached near one end of the bar 37. While, in practice, it is more advantageous to utilize the type of construction shown in Fig. l, in effect, the force exerted upon the bar 37 by the dangle roller 10 is the same as if the latter would be physically attached to the bar itself. It is seen that the angular position of bar 37 at the fulcrum point may be indicated by a pointer 43 cooperating with a scale 44 affixed to a stationary portion of the apparatus.

Let us first consider the start of winding operation, when the windup roller 11 has but a single wrap of material around it. The loop around the dangle roller 10 is then adjusted for a particular desired tension by moving the weight 38 and thereby determining the force exerted by the dangle roller 10 upon the material. The position of the bar 37 has a tilt to the left which is indicated by the pointer 43 over the scale 44. This tilt is sufficient to place a larger portion of the liquid medium 42 in the container 39 on the left side of the bar 37 so that the weight of this liquid is added to the effective weight of the dangle roller 10 and the liquid thus becomes part of the tension determining element.

As winding operations proceed, and the diameter of the roller 11 increases due to the material wound on it, the loop becomes shortened, the dangle roller 10 being lifted up which, in turn, as seen in Fig. 1, moves the electrical controller 28, lowering the speed of the motor 29 so as to wind the material at substantially the same speed as being fed by roll 18. As mentioned before, it is desirable in such operations to proportionately lessen the tension and this is accomplished by the gradual change in position of the fluid medium from the left end of the container to the right end. The weight of this fluid is slowly removed from the dangle roller and placed on the counterweight so that at the end of winding operation, as seen in Fig. 4, by the tilt of the bar 37, the force of gravity causes the liquid medium 42 to shift to the right side of the lever arm 37, adding its weight to the counterweight 38.

Without the fluid medium which allows automatic change of the efiective weight of the dangle roller, the windup tension would be constant from start to finish resulting in an undesirable mode of operation for the reasons stated hereinabove. It can easily be seen that by proper choice of volumetric capacity of the container or type of the liquid medium, various compensations may be made for the effective weight of the dangle roller during winding operation so as to obtain a desired ratio of tension change from start to finish. In casting film base material for. example, a 2 to 1 ratio was found satisfactory. The component elements of the tension control system in a practical embodiment had the following dimensions:

4 Length of bar 37 -;ins 50 Weight of dangle roller 10 lbs 30 Weight of counterweight 38 .lbs 10 The container 39 had a 1.4 gallons capacity. It was of cylindrical shape having a length of 44" and a diameter of 3". This was partially filled with water treated to arrest any bacterial growth.

It was also found expedient to smoothen the how of the liquid medium and avoid slushing which may take place as tension changes occur as the windup motor speed is controlled. This is accomplished by placing partitions or battles 45, 46 and 47 in the container 39 as seen in Fig. 7. These baflies are provided with small openings through which the liquid may pass. The numher and size of these bafiles may vary depending on the size and shape of the container and the liquid medium used.

A modification of the container is seen in Figs. 5 and 6, where, in place of a single container, use is made of the communicating vessel principle. The bar 37 may have a bucket-shaped vessel 50 at one end and a similar vessel 51 at the other end suspended so that movement of the bar will not change the angular position of the buckets. A communicating tube 52 which may be a flexible conduit interconnects the vessels 5t] and 51. As winding operations progress, the bucket 51 will be lowered and the liquid gradually transferred from the vessel 50 to the vessel 51, thereby transferring the weight in the same manner as described in connection with Figs. 2, 3 and 4.

It is also feasible to construct the bar 37 as a hollow bar which will accommodate the liquid. This construction eliminates the container 39 without changing the mode of operation described above.

I claim:

1. In a tension control system for web material wound from a supply roll over a plurality of rollers onto a takeup roll, said rollers including a dangle roller over which said material is looped, means for controlling the winding speed in accordance with the position of said roller whereby the effective weight of said roller determines the tension, adjustably operable means for weighting said roller and thereby predetermining the web tension at the start of winding, and gravity actuated means forautomatically decreasing the effective weight of said roller during winding upon a change in position thereof.

2. In a tension control system for web material wound from a supply roll over a plurality of rollers onto a takeup roll, said rollers including a dangle roller over which said material is looped, means for controlling the winding speed in accordance with the position of said roller whereby the effective weight of said roller determines the tension, adjustably operable means for weighting said roller and thereby predetermining the web tension at the start of winding, and gravity actuated means for automatically and gradually decreasing the etfective weight of said roller during winding upon a change in position I thereof.

3. In a tension control system for web material wound from a supply roll over a plurality of rollers onto a takeup roll, said rollers including a dangle roller over which said material is looped, means for controlling the winding speed in accordance with the position of said roller whereby the effective weight of said roller determines the tension, adjustably operable means for weighting said roller and thereby predetermining the web tension, at the start of winding, and gravity actuated means for auto matically and gradually decreasing the effective weight of said roller during winding upon a change in position thereof in proportion to the increase in diameter of said take-up roll.

4. In a tension control system for web material wound from a supply roll over a plurality of rollers onto a takeup roll, said rollers including a dangle roller over which said material is looped, means for controlling the windassess? ing speed in accordance with the position of said roller whereby the effective weight of said roller determines the tension, adjustably operable means for weighting said roller and thereby predetermining the web tension at the start of winding, and gravity actuated means for automatically and gradually decreasing the effective weight of said roller during winding upon a change in position thereof in proportion to the increase in diameter of said take-up roll, said last mentioned means being so dimensioned that the decrease in tension from start to finish of winding is in the order of 2 to 1.

5. In an apparatus for winding film base material, a supply roll, a plurality of intermediate rollers over which said material travels, a take-up roll, motor means for driving at least one of said intermediate rollers at a 'substantially constant speed, a motor for driving said take-up roll, an electric controller for controlling the speed of said motor, a tension control device including a lever bar pivotally supported at a fulcrum point, a dangle roller efiectively weighting said bar near one end thereof, said material being looped over said roller, a weight displaceahly supported on the other end of said bar for counterbalancing the weight of said dangle roller at the start of winding to a desired tension, means interconnecting said bar with said controller whereby the angular position of said bar etfectively controls the speed of said motor, and means for automatically altering the effective weight of said roller and thereby the tension of said material during winding comprising an elongated container attached to said bar and in parallel therewith, a fluid medium in said container, said fluid medium being displaceable by gravity upon change in the angular position of said bar.

6, Apparatus in accordance with claim 5 wherein said container is of tubular shape, closed at both ends.

7. Apparatus in accordance with claim 5 wherein said container is of tubular shape, closed at both ends, having spaced partitions for regulating the flow of liquid medium.

8. Apparatus in accordance with claim 5 wherein said container comprises a pair of communicating vessels, one being suspended near one end and the other near the other end of said bar.

9. Apparatus in accordance with claim 5 wherein the volume of said container is so chosen that, with a given liquid medium, the tension is lowered from start to finish of winding in a proportion of 2 to 1.

References Cited in the file of this patent UNITED STATES PATENTS 672,745 Stonemetz Apr. 23, 1901 1,691,294 Lewellen Nov. 13, 1928 1,968,636 Dickhaut July 31, 1934 2,208,340 Parsons July 16, 1940 2,331,765 Carter Oct. 12, 1943 2,720,093 Lambach et a1 Oct. 11, 1955 

